Harmonic producer system



Feb. 7, 1939. M. E. CAMPBELL Er' AL 2,146,053

HARMONIC PRODUCER SYSTEM Filed July "51, l93'7 5 f Co 16 Ro MECAMPBELL INVEN7URS-J' M WEST I Patented Feb. 7, 1939' MarkECam Peqnannock, and Julian M. I

P Welt, Bidgewood, N. 3., assignors to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application July 31, 1931, Serial No. 158,706

' 5 Claims. 101. 172-281) This invention relates to a harmonic producing system and more particularly to circuit modifications for improving the power efliciency of such system.

5 The copending application of L. R. Wrathall, Serial No. 77,989, filed May 5, 1936, now Patent No. 2,117,752, dated May 17, 1938 and assigned to applicants assignee, discloses a magnetic harmonic producing system for generating and se- 10 lecting a predetermined group of odd and even harmonics having uniformly large amplitudes. In that system it was found that in using 'ordi-' nary harmonic selective networks there was a difierence in the power outputs of the various 15 harmonics. This invention is concerned'with the provision of optimum load impedances to obtain maximum outputs of all harmonics produced in such a system.

It is an object of the invention to equalize the 20 outputs of both odd and even harmonics.

It is another object of the invention tovary the output of a preselected harmonic relative to the otherharmonics in a group.

It is a further object of the invention to obtain 25 maximum outputs of all harmonics.

The aforementioned copending application of L. R. Wrathall discloses a harmonic producing.

system having a non-linear coil and an alternating current generator for impressing a fundamental frequency thereon, and an output circuit for the coil including a condenser, copper-oxide bridge and filter banks to produce and select a certain group of odd and even harmonics. In the present invention, each filter in the odd and 35 even banks is initially devised with .the same impedance and the two banks are coupled to the output circuit by a pair of transformers.: The

turn ratios of the transformers are so preselected 50 The invention will be readily understood froml the following description taken together with the drawing which illustrates the invention in its preferred form.

Referring to the drawing, analternating cur- '5 rent generator in impresses a wave of fundamendesigned to select a certain even harmonic.

tal frequency, for example, four kilocycles, on a primary circuit l i comprising a tuned circuit l2 and a saturable-core inductance i3 connected in series. A secondary or output circuit l4 including a condenser 20 is coupled througha transformer 5 l5 to a filter bank It and through a shunt rectifier-bridge i1 and a coupling transformer It to a filter bank i9.

As explained in the copending application 01" L. R. Wrathail, supra, a proper selection of the constants of the inductance ll, condenser 20 and the elements comprising the filter banks produces a desired group of odd and even harmonics hav-' ing substantially uniform amplitudes. Each filter of the bank- IG is designed to select a certain odd harmonic, while each filter of the bank is is Each filter bank is arranged for parallel operation and may include any number of individual filters. In

practice it was found that due to power losses in the rectifier-bridge the 'even harmonic outputwas' less than the odd harmonic output.

In the preferred embodiment of the invention, the constants of the condenser Co, inductance Io and resistance R0 and of the condenser C1, in-

ductance In and resistance Rn comprising the individual filters of the odd and even banks, respectively, are initially fixed at the same value so that the filter terminating impedance is the same for all harmonics. As the odd and even filter banks 7 are coupled to the generator l0 throughthe respective transformers i5 and I8, the turn ratios of these transformers are so selected relative to each other that the load impedances looking from the generator ill have such values as will produce 5 equal outputs of both odd and even harmonics. With the turn ratios thus proportioned, a further selection to obtain the absolute turns will produce maximum outputs of all harmonics. 'I'hus the absolute turn ratios of the coupling trans- 40 formers together with the uniformity of the individual filters provides optimum load impedances whereby the odd and even harmonic outputs are not only equalized but are also produced at their maximum values. It is understood that the determination of the absolute turn ratios includes compensation in the even branch for losses dissipated in the rectifier-bridge.

with the outputs of odd and even harmonics equalized in the aforedescribed manner. the resistance R0 in one of the filters of the odd harmonic filter bank, say filter 2!, may be fixed at a value less than that for the corresponding element in the other filters of this bank. This decreases the impedance termination for the odd harmonic assigned for selection 'by that particular filter. The output of that harmonic is therefore increased above the outputs of the other filters in the same ratio as the impedance is decreased. Similarly, an increase in the output of any even harmonic may be obtained by decreasing the resistance R: in one of the filters included in the even bank. Accordingly, the output of a particular odd or even harmonic or both can be increased by decreasing the respective filter resistances R0 or Rs. It is obvious that an increase in the impedance of a particular filter will cause a decrease in the harmonic output therefrom.

A still further increase, in equal amounts of the outputs of both odd and even harmonics can be obtained by connecting a condenser 2i across the output circuit. Proportioning that condenser together with the condenser 20 to optimum values will more than double the odd and even harmonic outputs obtained with the circuit 'disclosed in the copending application of L. R. Wrathall, supra. The condenser 2| may also be connected in the output circuit at any one of the following points: (a) in bridge of the primary winding of transformer I5, (b) in bridge of the secondary winding of transformer 15, and (c) in bridge of the secondary winding of transformer It. the sixteenth through the twenty-seventh harmonic of a frequency of four kilocycles, the optimum values of condensers 20 and were 0.014 and 0.0055 microiarad, respectively. These condenser values will vary depending on the range of harmonics that is produced.

While the invention is described in connection with a harmonic producing system utilizing a saturable-core inductance, it is to be understood that it is equally applicable to similar systems employing other types of non-linear distorting elements such, for example, as those using thyrite, copper-oxide, vacuum and gas tubes.

What is claimed is:

l. A harmonic producing circuit comprising a distorting device, a source of alternating current of fundamental frequency, circuit means for applying the fundamental frequency to said distorting device so as to produce therein a group of harmonics of the fundamental frequency, an output circuit for said distorting device, and means for substantially increasing the output of the entire group of produced harmonics comprising capacity of substantially optimum value effectively connected in shunt of said output circuit.

With a distorting circuit producing 3. A'harmonic producing circuit comprising a distorting device, a source of alternating current f fundamental frequency, means for applying he fundamental frequency to said distorting device so as to produce therein a group of harmonics of the fundamental frequency, an output circuit for said distorting device including a capacity and a substantially resistive load in series with said distorting device for making certain that the harmonics in the produced group have uniformly large outputs, and means comprising capacity connected in said output circuit in bridge of the first mentioned capacity and said distorting device and proportioned to substantially increase the outputs of the harmonics in the entire group of produced harmonics.-

4. The harmonic producing circuit according to claim 3' in which the second mentioned capacity is proportioned to at least double the outputs of the harmonics in the entire group of pro-- duced harmonics.

5. A harmonic producing circuit comprising a distorting device, a source of alternating current of fundamental frequency, means for applying the fundamental frequency to said distorting device so as to produce therein a group of odd harmonics of the fundamental frequency, an output circuit for said distorting device including a capacity and a substantially resistive load in series with said distorting device for making certain thatthe odd harmonics in the produced group have uniformly large outputs and means for eiiecting from the produced odd harmonics a group of even harmonics having uniformly large outputs, and means comprising capacity connected in the output circuit in bridge of the first mentioned capacity and said distorting device and proportioned to substantially increase the outputs of the harmonics in the groups of both odd and even harmonics.

MARK E. CALIPBEIL. JULIAN M. WEST. 

